The current trend in the computer industry toward smaller IC device features, necessitated by more complex, cost effective and higher speed circuits is well known. The corresponding requirements in terms of surface preparation and processing have also changed at an even faster rate. For example, as photolithographic features shrink below one micron, and depth-to-width ratios increase, wafer cleaning and drying in these feature "trenches" becomes a process limiting factor. Reduction of particulate and minimizing particulate contribution of the equipment itself becomes more increasingly important. Sonic wave energy has demonstrated an ability to enhance the effectiveness of liquid processing solutions to reduce particulate in many cases due to micro cavitation or shear forces. Processing enchancement techniques in the form of high frequency sonic wave energy in combination with established chemistries is thus provided by the present invention to meet these needs.
In the areas of production and process control, single substrate wafer handling provided by the present novel sonic processing module, method and system provides distinct advantages over previously available sonic processing techniques in uniformity of environment, exposure to processing, using minimal amounts of processing solution, and processing results. In the single wafer process module of this invention, control of processing liquid and sonic wave energy flow can be easily repeated and uniformly applied. The single wafer is supported within the chamber on its periphery to minimize surface contact and have both surfaces exposed to the processing solution and the sonic wave. Further, according to the present invention, a plurality of the presently disclosed individual modules can be combined to provide a single sonic processing system to provide for simultaneously processing a plurality of wafer substrates. In addition, automation of process information, and wafer identification tracking can be accomplished easily in the random access, single wafer process.
There have previously been available techniques for processing semiconductor wafers and other substrates immersed in liquid processing solution with the use of sonic energy. Descriptions of megasonic processing apparatus and methods are found in U.S. Pat. Nos. 3,893,869; 4,099,417; 4,118,649; 4,326,553; 4,543,130; 4,736,760 and 4,804,007. While these previously available sonic processing apparatus and methods have been satisfactory in some respects, there is still need for improvements, particularly in protecting the sonic wave generating source from the harsh liquid chemical processing environment, in amplifying and concentrating the sonic wave energy to enhance its processing effect, in minimizing the size of the process chamber itself, and in terms of the other needs of the computer industry discussed herein above.